The inventive subject matter relates to colorants for fibers, textiles and other substrates. It particularly relates to the application of natural or synthetic colorants to textile surfaces. The inventive subject matter may use plasmas generated in atmospheric pressure systems to facilitate coloration of substrates.
The textile material may be in one of several forms such as fiber, yarn, fabric, garments, etc. Textile colorants are supplied in both solid and liquid forms, for example, as powders, granules, solutions or dispersions. In certain instances, precursors are applied to textile materials to generate the colorant in situ within the textile.
Textile colorants impart color to a textile material, usually with a high degree of permanency, as a result of their chemical binding or physical entrapment within or around the textile material. Both dyes and pigments are used in the coloration of textiles. The former substances are present in solution at some point during their application, whereas pigments remain insoluble within any vehicle in which they are applied as well as within the textile material itself. A dye has an affinity for a textile material and is soluble in a suitable solvent for application to a given substrate. Dyes can penetrate the fiber for dyeing where pigments are fixed to the surface. Dyes are attracted to the fibers because of the chemical interactions between the fibers and the dye. Reactive groups attached to a chromophore (color molecule) provide the capability of the dye to react with the fiber without affecting the color. Bonds can be formed by hydrogen bonds, ionic bonds, or covalent bonds. The complex interactions of and variables in dyeing have been well documented. Areas of variability include substrate, chemicals, preparation of substrate, and procedure variations.
Pigments impart color; however, pigments do not have an inherent affinity for textile material. Where dyes can diffuse into the fiber material, pigments are bonded to the fiber surface. In some cases the name can differ by whether the colorant is suspended or dissolved in the solution.
Current dye techniques for textiles use large amounts of water to apply the dye. The fabric must first be wet to help the dye to penetrate into the fabric. These wet processes also use a large amount of heat and energy to cure and set the dye. After the fabric is removed from the dye, the fabric is then heated to remove the moisture and affix the dye permanently to the fibers in the fabric. It is known that before application of any dyes, fabrics can be pretreated via atmospheric plasma to condition or activate the fabric surface for improved dye pickup during typical wet processing. Color fastness, cure temperature reduction, and wettability/hydrophilicity may each be improved following appropriate atmospheric plasma pretreatment. However, such pretreatments still use and are subject to all the disadvantages of the conventional, water intensive dye-bath procedure. Contributing to the disadvantages of the water-carrier approach, other chemicals must be added to control the pH, alkalinity, and other parameters of the bath.
Traditionally, water has been used as the dyeing medium between fiber and dye interactions. Hydrophilic fibers absorb water (this breaks internal fiber hydrogen bonds, and causes the fiber to swell with water. This allows dyes to migrate into the fiber and bond with the fiber. When the water temperature is increased, fiber swelling increases and better dyeing results with an increase in temperature. Hydrophobic fibers, polyesters and polyamides, do not swell in water. Therefore, the water serves as a medium to transfer small dye particles to be deposited onto the fiber surface. In this case water can serve as a heat transfer medium.
Applying a textile finish commonly involves passing a fabric (woven, knitted, or nonwoven) through a chemical bath, followed by a thermal curing process. In the chemical bath, the fabric collects or absorbs, some of the chemicals in the bath. These chemicals are commonly called “finishes” that include water repellents, anti-microbial, UV protection, and colorants. To assist with the solubility of the chemical finishes in the chemical bath, surfactants and emulsifiers are often added to create uniform suspensions in the bath.
Currently, wet processes used with textiles have several disadvantages. The drying and curing of the treated fabric requires the fabric to be exposed to several minutes at high temperatures. Large ovens and frames may be required to prevent fabric from shrinking, while the high temperatures may alter the drape and stiffen the fabric, or create a dry and rough hand feel. Additives required to solubilize the finish in the bath may penetrate the fabric, leave breakdown products, create a thin film, or remain as impurities. Some impurities may not wash off and result in the removal of the finish during certain home cleaning practices. Because the composition of the chemical bath and pH change over time as the finish is absorbed onto the fabric, the bath must be periodically replaced. This comes at a cost to the chemicals used process as well as the environment, if not properly filtered. Further, dye bath chemistry must be constantly monitored and adjusted. Large amounts of water are used during these finishing processes, as well as energy to cure the fabric at relatively high temperatures. In addition, at each step in the process there is specialized equipment and steps—bath, ovens, cleaning and recycling of baths and water. The required equipment for all the steps occupies a sizeable footprint on the factory floor, adding to the complexity and expense of operations.
Other areas having a need for efficient and simplified construction of end products with multiple properties include bed linens, table linens, upholstery, drapery, tents, awnings, etc.
Accordingly, there is a substantial need for improved textile colorant applications and constructions and manufacturing methods that address the aforementioned needs. These and various other needs are addressed by the inventive subject matter disclosed herein.